The present invention relates to a printing drum to be mounted in a printing machine such as, for example, a mimeographing machine, as well as a method for producing the same.
FIG. 4 illustrates a conventional printing drum 10 mounted in a mimeographing machine. The printing drum 10 has a cylindrical, peripheral wall 1 in which there are formed a large number of fine holes for the passage of ink therethrough. Inside the peripheral wall 1 is disposed an ink feeder though not shown. On the outer peripheral surface of the cylindrical, peripheral wall 1 is provided a stencil clamping means 2 in parallel with the axis of the peripheral wall 1.
Further, two ink-permeable screens 11 and 12 are wound one upon the other around the outer peripheral surface of the peripheral wall 1. The screens 11 and 12 operate for dispersing the ink which has passed through the fine holes of the peripheral wall 1 uniformly throughout the whole of the printing area on the printing drum and also function to hold an appropriate amount of the ink to make clear and uniform printing as much as possible. The screen 11 as an inner screen is of a relatively large mesh, while the screen 12 as an outer screen is of a relatively small mesh.
End portions of both screens 11 and 12 are fixed to the clamp means 2 with bolts 13 or the like. The screens 11 and 12 are put one upon the other and wound around the peripheral wall 1. The opposite end portions of both screens 11 and 12 are provided with elongated strip-like edge members 14 and 15, respectively. As shown in FIG. 5, both side portions of the edge members 14 and 15 are connected together by means of clip members 16. The edge members 14 and 15 thus rendered integral with each other are then mounted to the clamp means 2 through springs 17, as shown in FIG. 6. Both screens 11 and 12 are brought into close contact with the outer peripheral surface of the peripheral wall 1 by the biasing force of the springs 17.
For performing the operation of winding the screens 11 and 12 around the peripheral wall 1 and then fixing them with springs 17, the printing drum 10 is fixed onto a fixing jig 20, as shown in FIG. 4.
According to the conventional printing drum 10 described above, there has been the problem that the construction for mounting the screens 11 and 12 onto the peripheral wall 1 is complicated, the number of components is large, and it is necessary to provide a special jig.
Further, since the springs 17 have a strong biasing force, if they are not securely mounted in the spring mounting operation, they may be disengaged and cause an accident of injury. Thus there has been the problem that the drum assembling work involves danger.
It is the object of the present invention to bring an ink-permeable screen into close contact with the outer peripheral surface of the printing drum peripheral wall, using an extremely simple and safe construction.